The Effects of Intercritical Heat Treatment of the SA508 Grade 3 Class 1 Steel Before Welding on the Mechanical Properties in Its Welded Joint

Abstract

In order to improve the toughness in the welded heat affected zone (HAZ) of the SA508 Grade 3 Class 1 steel, the intercritical heat treatment (IHT) has been applied before the welding. The application of the IHT before welding resulted in the decrease of fracture appearance transition temperature (FATT50) and 68Joule transition temperature (vTr68). The improved effects of the IHT on the mechanical properties of this steel have been consistently preserved in the HAZ and the effect of the IHT before welding on the transition temperatures in the HAZ of this steel was much better than those of base metal. These positive results were closely related with the newly formed sub-grains, the spheoridized carbides precipitated at sub-grain boundaries and lath boundaries which would have been acted as obstacles to the cleavage propagation.